1. Field of Invention
The present invention relates to a diffuser assembly for finely dispersing gases or liquids and a method of forming the same.
2. Description of Related Art
Diffuser assemblies are used in a variety of application to finely disperse gases or liquids into other liquids. Ozone gas, for example, is sometimes diffused through a diffuser assembly into water for the purpose of purifying the water. In wastewater treatment applications, wastewater is collected in a large pond, tank or basin. A manifold structure that includes a series of supply pipes arranged in an array is typically installed near the bottom of the pond, tank or basin. One or more diffuser assemblies are connected to the supply pipes at various locations to provide a substantially uniform pattern of gas dispersion throughout the lower portion of the volume of the water being treated.
The principal operative component of each diffuser assembly is a gas permeable porous diffuser element that is in communication with a chamber situated within the diffuser assembly. Gas such as ozone is supplied under pressure through the supply piping causing pressurized gas to fill the chamber. The pressure forces the gas to permeate through the interstices of the porous diffuser element into the water being treated. The gas enters the water in the form minute bubbles or microbubbles, which have a larger surface area per unit volume than bubbles of larger size. Generally speaking, the finer the bubbles that can be diffused into the water the better, because finer bubbles provide a more optimal surface area of gas exposed to the water being treated.
The diffuser element, which is sometimes referred to as a sparger in the industry, is generally formed of a gas permeable, porous material. Because of the corrosive nature of ozone, it has been found that an advantageous material for the diffuser element is a porous ceramic. This material is not vulnerable to the corrosive effects of either the sewage or of ozone gas.
One type of diffuser element made from porous ceramic material is described in U.S. Pat. No. 4,046,845, which is hereby incorporated by reference in its entirety. The diffuser assembly described in that prior art reference essentially comprises two components: (1) a relatively dense base portion that may be formed of a PVC plastic material or stainless steel; and (2) a porous ceramic diffuser element in the form of a relatively flat circular plate that seats in an annular groove or rabbet formed in the base member. The base member and the interior surface of the ceramic diffuser element define an interior chamber that is supplied with gas through an inlet tube connected to a gas supply pipe.
In this device, a seal ring formed of organic material, such as an elastomer, is positioned at the joint between the base and the outer edge of the ceramic diffuser plate. A threaded metal fastener extends through a central opening in the ceramic plate and is anchored to the base. The fastener is formed of steel and has an organic seal ring positioned between the fastener head and the upper surface of the ceramic plate.
The advantage of this construction is that the porous ceramic material provides an excellent means for diffusing minute bubbles into the liquid being treated, while at the same time, being formed of material that resists the corrosive effects of the environment including reactive gases that are being diffused. One disadvantage of this construction, however, is that the diffuser assembly includes components that are formed of materials that are vulnerable, over a period of time, to the corrosive effects of the environment it is being used in. Ozone gas is the highly corrosive, and over time the metals and/or organic plastic components in the diffuser assembly eventually fail due to corrosion damage.
U.S. Pat. No. 5,863,031, which is hereby incorporated by reference in its entirety, describes a diffuser assembly that does not include metal components, which are subject to corrosion damage. The diffuser assembly described therein comprises a housing formed of a dense ceramic material having a floor with a central inlet opening formed therein, an inlet fitting secured to the floor, and a diffuser plate formed of a porous ceramic material cemented to the top portion of a wall of the housing. This diffuser assembly, while superior to prior art diffuser assemblies, is also subject to some limitations.
Since there are no gaskets or other compressible materials used, the porous ceramic diffuser element must be cemented “hard and fast” to the top of the wall of the housing. The bond or joint formed between the diffuser element and the housing using the cement is strong, but it is also brittle. In some situations, this bond can break when the diffuser assembly is packaged, shipped, unpacked or installed. In addition, vibrations caused by the gas supply equipment can also jar the diffuser assembly enough to cause the cement joint to fail.
In addition, the inlet or fitting portion of the device described in U.S. Pat. No. 5,863,031 is typically formed of a fluorocarbon polymer. While this material is more resistant to the corrosive effects of ozone gas than some other materials, it still does not have the resistance and durability provided by inorganic ceramic materials.